Cob building is a variation on the mud brick idea, and can be referred to as a cob brick. Indigenous earth is mixed by hand (or more traditionally, by using the feet) into a mud, then long straw is added. The proportion of straw to mud for a cob brick is greater than that used for baked bricks. The gloppy mixture is then piled and sculpted into dwellings.
Handfuls of the cob mixture can be tossed from worker to worker, eliminating the need for machinery such as cranes. It is a very durable kind of construction; centuries-old cob houses are still standing in parts of the British Isles.
Because earth is available everywhere obviously, some variations of cob housing has been found in many parts of the world throughout history. A variation of this is a kind of cob structure where the mud used is quite thin, and just enough of this thin mud is used to stick long straw strands together. This mostly-straw mixture is tamped into a mold or frame, and when it hardens, the frame is removed. Such “light straw/clay” buildings are more insulating that traditional cob, but not as structurally sound. Walls that are mostly straw, even with mud mixed in, cannot bear that much weight.
A traditional cob build is not suitable for areas of the world where there are temperature extremes. For temperate climates, however, cob structures can provide strong, dry, durable dwellings that lend themselves to creative shapes. Therein lies cob’s charm: artistic builders can create sculptural buildings in creative, organic shapes. There are few limitations to the design of a cob structure.
A cob build is labor-intensive, and they take quite a bit of time and effort to build. The walls need to “cure,” a process that can take up to a year. And not everyone likes a curvy, sculptural home.
Cob houses are of course very eco-friendly. Their mud and straw construction to make a cob brick does not use any non-renewable resources, nor does a cob build process require any fossil fuels (no machinery is necessary). It is also extremely economical; cob houses can be built for less than $1000. One famous proponent of cob housing built his cob home for around $500.
A great deal of professional skill is not required. The internet, libraries and bookstores carry all kinds of how-to information on cob buildings. Cob building techniques is one that is making a comeback. We hope our explanation of a cob house, cob structure and cob building will help you with your new cob housing.